Research On Medical Image Cryptosystem Based On Compound Chaos Theory

Medical image information security has become a hot topic in today’s society.Medical image information is characterized by a large amount of data.When using traditional cryptographic systems to transmit medical images,security and encryption and decryption speed cannot be considered at the same time.The non-dynamic characteristics of chaotic systems meet the scrambling and diffusion characteristics required in cryptography.Therefore,designing safe and efficient medical cryptographic systems based on chaotic systems has become an important research direction at present.The security performance and encryption and decryption efficiency of the medical image encryption system designed based on chaos theory are related to the performance of the chaotic system,scrambling algorithm,and diffusion algorithm used.Traditional one-dimensional chaotic systems have the problems of small key space,breakpoints in chaotic intervals,and uneven distribution of output chaotic sequences.In view of the above problems,this paper combines the existing chaotic systems in parallel and cascaded appropriately.Using Matlab simulation software to test the designed composite chaotic system,the experiment proved that it has the characteristics of high Lyapunov exponent,wide and continuous chaotic interval,uniform chaotic sequence distribution,and large key space.It can be used as a chaotic sequence generator in the medical image password system.In the medical image encryption system,the ciphertext image generated by the traditional scrambling algorithm and the diffusion algorithm has low randomness.Based on this problem,the improvement measures are proposed,the "uniform scrambling" and"blocking" methods are introduced,the pixels in each block are evenly scrambled into each pixel block,and the block diffusion technology is used for the image after the scrambling algorithm,That is,the pixel points are divided into three parts to design the diffusion algorithm separately.Use Matlab simulation software to draw the encrypted ciphertext image and calculate the information entropy.The experimental results show that the improved diffusion algorithm and scrambling algorithm can effectively improve the randomness of the encrypted image,which is embodied in the value of the information entropy statistics of 7.9992.Approaching the theoretical value.Input the medical plaintext image and key into the designed medical image encryption system based on compound chaos,and use Matlab to test the security and encryption and decryption efficiency of this system.The time consumed for encryption and decryption of this system is 0.4-0.7s.The key space is 2265,the information entropy is between 7.9993-7.9998,and the indicators are good.The test results show that this system is a medical image encryption system with practical application value.